Inorganic materials such as silicon oxides or nitrides have been mainly utilized in the information and electronic industries. Recent technical developments and demands for compact and high efficiency devices need new high performance materials. In this respect, a great deal of attention has been paid to polymers which have desirable physicochemical properties such as low dielectric constant and moisture absorption rate, high adhesion to metals, strength, thermal stability and transparency, and a high glass transition temperature (Tg>250° C.).
Such polymers can be used as insulating films of semiconductors and TFT-LCDs, protective films of polarizing plates, multi-chip modules, integrated circuits (ICs), printed circuit boards, molding materials for electronic components, optical materials, e.g., flat panel displays, and the like. As one of new performance materials, cycloolefin polymers exhibit much improved properties than conventional olefin polymers, in that they show high transparency, heat resistance and chemical resistance, and have a low birefringence and moisture absorption rate. Thus, cycloolefin polymers can be applied to various applications, e.g., optical components such as CDs, DVDs and POFs (plastic optical fibers), information and electronic components such as capacitor films and low-dielectrics, and medical components such as low-absorbent syringes, blister packagings, etc.
Cycloolefin polymers are known to be prepared by one of the following three methods: ROMP (ring opening metathesis polymerization), copolymerization with ethylene, and addition polymerization using catalysts containing transition metals such as Ni and Pd. These methods are depicted in Reaction Scheme 1 below. Depending on the central metal, ligand and cocatalyst of a catalyst used in the polymerization reaction, polymerization characteristics and the structure and characteristics of polymers to be obtained may be varied.

A Polymer prepared by the ROMP method has one double bond per one monomeric repeating unit, thus, the polymer has poor thermal and oxidative stability and is mainly used as thermosetting resins. U.S. Pat. No. 5,011,730 issued to Tenny et al. discloses that such thermosetting resins are fabricated into printed circuit boards by reaction injection molding.
In order to improve physicochemical properties of polymers prepared by the ROMP method, a method of hydrogenation of the ROMP-polymer in the presence of Pd or Raney-Ni catalysts has been proposed. Hydrogenated polymer shows improved oxidative stability, but still needs to be improved in its thermal stability. Further, a cost increased due to additional processes is against its commercial application.
Ethylene-norbornene copolymers are known to be first synthesized using a titanium-based Ziegler-Natta catalyst by Leuna, Corp., (German Patent No. 109,224 issued to Koinzer, P. et al.). However, impurities remaining in the copolymer deteriorates its transparency and its glass transition temperature (Tg) is very low, i.e., 140° C. or lower. Although it was reported that the use of a zirconium-based metallocene catalyst enables the synthesis of high molecular weight of polymers having a narrow molecular weight distribution (Plastic News, Feb. 27, 1995, p. 24), as the concentration of a cycloolefin monomer in a reaction medium increases, the catalytic activity decreases and a copolymer to be obtained has a low glass transition temperature (Tg<200° C.). In addition, the copolymer has poor mechanical strength and chemical resistance, particularly against halogenated hydrocarbon solvents.
U.S. Pat. No. 3,330,815 discloses a method for preparing cycloolefin polymers in the presence of a palladium-based catalyst. However, molecular weight of the cycloolefin polymer is reported to be 10,000 or less. Gaylord et al. reported a polymerization of norbornene using [Pd(C6H5CN)Cl2]2 as a catalyst (Gaylord, N. G.; Deshpande, A. B.; Mandal, B. M.; Martan, M. J. Macromol Sci.-Chem. 1977, A11(5), 1053-1070). Furthermore, Kaminsky et al. reported a homopolymerization of norbornene by using a zirconium-based metallocene catalyst (Kaminsky, W.; Bark, A.; Drake, I. Stud. Surf. Catal. 1990, 56, 425). These polymers have a high crystallinity, thermally decompose at a high temperature before they melt, and are substantially insoluble in general organic solvents.
Adhesion of polymers to inorganic surfaces such as silicon, silicon oxide, silicon nitride, alumina, copper, aluminum, gold, silver, platinum, nickel, tantalum, and chromium is often a critical factor in the reliability of the polymer for use as electronic materials. U.S. Pat. No. 4,831,172 discloses a benzocyclobutene (BCB)-functionalized organosilane adhesive aid to increase the adhesion between an inorganic surface and a polymer.
The introduction of functional groups into a norbornene monomer enables the control of chemical and physical properties of a resultant norbornene polymer. U.S. Pat. No. 3,330,815 discloses a method for producing polynorbornenes from norbornene monomers containing polar functional groups. However, catalysts are inactivated by the polar functional groups of norbornene monomers, which results in an earlier termination of the polymerization reaction, thereby producing a norbornene polymer having a molecular weight of 10,000 or less.
In an effort to overcome these problems, a method for polymerizing norbornene derivatives containing polar functional groups after pretreating the norbornene derivatives with silane, alkylaluminum or borane compounds was suggested by Fink, G. et al. (Macromol Chem. Phys. 1999, 200, 881). This method is, however, limited in the introduction of the pretreated norbornenes into a polymer chain and in increasing a polymerization activity. In addition, this method further requires a post-treatment step for removing the silane, aluminum or borane compound.
U.S. Pat. No. 5,179,171 discloses a copolymer comprising polymerized units from ethylene and polymerized units from at least one cycloolefin, in which cycloolefin is incorporated in the polymer chain without ring opening in the presence of a catalyst which is formed from a soluble vanadium compound and an organoaluminum compound. However, the polymer thus prepared is thermally unstable, and general physical and chemical properties of the polymer, and its adhesion properties to metals are not greatly improved.
Researches have been carried out in the polymerization of norbornenes containing an ester, acetyl or silyl group, in association with the introduction of polar functional groups (Risse et al., Macromolecules, 1996, Vol. 29, 2755-2763; Risse et al., Makromol. Chem. 1992, Vol. 193, 2915-2927; Sen et al., Organometallics 2001, Vol. 20, 2802-2812; Goodall et al., U.S. Pat. No. 5,705,503; Lipian et al., U.S. Pat. No. 6,455,650).
Sen et al. reported a method for polymerizing various ester norbornene monomers in the presence of a catalyst, [Pd(CH3CN)4][BF4]2, in which exo isomers were selectively polymerized, and the polymerization yield was low. (Sen et al., J. Am. Chem. Soc. 1981, Vol. 103, 4627-4629).
U.S. Pat. No. 5,705,503 issued to Risse and Goodall, et al. discloses a polymer prepared from norbornenes containing polar functional groups, in which a majority of the monomer consist of endo-isomers. However, in the polymerization reaction in which polar norbornene derivatives containing only ester groups are polymerized, the molar ratio of a catalyst to the monomers is about 1/100, which is economically disadvantageous.
In the polymerization reaction of polar functional norbornenes containing ester groups or acetyl groups, it has been reported that an excess of the catalyst is required ( 1/100 to 1/400 relative to the monomer) and the removal of the catalyst residues after polymerization is difficult. U.S. Pat. No. 6,455,650 issued to Lipian et al. discloses a method for polymerizing norbornene derivatives in the presence of a small amount of a catalyst. However, the product yield in a polymerization of a polar monomer such as an ester-norbornene, is only 5%.
Sen et al. reported a method for polymerizing an ester-norbornene in the presence of a catalyst system including [(1,5-Cyclooctadiene)(CH3)Pd(Cl)], PPh3, and Na+[3,5-(CF3)2C6H3]4B−, in which the polymerization yield of ester-norbornenes is 40% or lower, the molecular weight of the polymer is 6,500 or lower, and the molar amount of the catalyst used is about 1/400 based on the monomer (Sen et al., Organometallics 2001, Vol. 20, 2802-2812).
Risse et al. reported a method for polymerizing a methylester-norbornene in the presence of [(η3-ally)PdCl]2 and AgBF4 or AgSbF6 as a catalyst (Risse et al., Macromolecules, 1996, Vol. 29, 2755-2763). The polymerization yield is about 60%, and the molecular weight of a resultant polymer is about 12,000. In addition, an excess of the catalyst of about 1/50 by mole, based on the monomer is used. The reason for the use of an excess of the catalyst is explained by the fact that polar functional groups of the monomers such as ester or acetyl groups are coordinated to the active sites of the catalyst, causing steric hindrance effects preventing the norbornene derivatives from approaching onto the active sites, or cationic active sites are electrically neutralized by the polar functional groups, causing a weak interaction with the double bond of norbornene (Risse et al., Macromolecules, 1996, Vol. 29, 2755-2763; Risse et al., Makromol. Chem. 1992, Vol. 193, 2915-2927).
Therefore, conventional methods for polymerizing cycloolefins containing polar functional groups fail to meet a certain desired level in the aspect of polymerization yield, a molecular weight of a resultant polymer, and a molar ratio of a catalyst to monomers.